Asthma
/Asthma is a common disorder of the lung where inflammation causes the bronchi to swell and narrow the airways (ie. bronchospasm) . This leads to reversible, recurrent airway obstruction. Symptoms include wheezing, shortness of breath, or difficulty breathing, which are often associated with “triggers” → at night, during exercise, with allergens (ie. infection, animals, mold, smoking, pollen, etc).
Let’s talk through asthma and how to treat it!
How do I diagnose asthma?
History - wheezing, cough, shortness of breath, chest tightness; temporal relationships and triggers
Physical - wheezes on auscultation
Should be confirmed by demonstrating airway obstruction on spirometry that is at least partially reversible
Pulmonary function tests!
FEV1 forced expiratory volume in 1 second
>12% increase in FEV1 after bronchodilator = asthma
FVC forced vital capacity (basically all the air that you can breathe out)
Normal FEV1/FVC ratio is around 75%, but predicted normal values can be calculated based on age, sex, and height
Asthma is an obstructive process, so FEV1/FVC ratio will be reduced
This is opposed to a restrictive process, where the FEV1/FVC ratio is not reduced, but both FEV1 and FVC ARE reduced about equally)
How does asthma change in pregnancy / why do we care about it in pregnancy?
Oxygen is good for everyone!
Goal is adequate oxygenation of the fetus and prevent hypoxic episodes in pregnant person
Poorly controlled asthma may be associated with increased prematurity, need for C/S, preeclampsia, growth restriction, other perinatal complications, and maternal morbidity/mortality
How do I classify asthma?
Check out Practice Bulletin 90!
How do I treat asthma?
In general:
Avoid factors that precipitate attacks (ie. allergens, smoke, pollen)
Get consultants on board if complex or difficult! (i.e., medicine/pulmonary)
Mild intermittent asthma - albuterol as needed, no daily meds
Mild persistent asthma - add low dose inhaled corticosteroids
Additional alternatives that could be considered are things like Cromolyn, leukotriene receptor antagonist, or theophylline
Moderate persistent asthma - add long-acting beta agonist (i.e., salmeterol) alongside low dose inhaled corticosteroid / increase to medium-dose inhaled corticosteroid (if needed) / medium-dose inhaled steroid and salmeterol
Severe persistent asthma - High-dose inhaled corticosteroid and salmeterol, and if needed, oral corticosteroid
Assessment of acute asthma
Medical history and exam (as always)
Examine airway function and fetal well-being if after 24 weeks
Patients with FEV1 measurements >70% for >60 minutes can usually be discharged if not in distress
Can order VBG if you want to get a gas, and can likely keep in ED for treatment if FEV1 <70% but >50%
However, if FEV1 <50%, may need admission
If patient becomes more drowsy, poor response, severe symptoms, confusion or PCO2>42mmHg, this may be a reason to admit to ICU
Treatment of acute asthma (in ED or in OB triage)
Oxygen for saturation >95%; measure spirometry at bedside with respiratory therapy.
Inhaled short-acting beta2 agonist by nebulizer or metered dose inhaler
Oral systemic corticosteroid if no immediate response.
If patients have FEV1 that is <40%, may need high dose inhaled short-acting beta2 agonist + ipratropium by nebulizer every 20 minutes or continuously for 1 hour and oral corticosteroids
If impending respiratory arrest - intubation and mechanical ventilation — get critical care, pulmonary, and/or anesthesia on board!
If improved / discharging: short-acting inhaler (i.e., albuterol) 2 puffs every 3-4 hours as needed and oral corticosteroids 40-60mg for 3-10 days. No need for tapering the steroid!
Ensure post-discharge follow up within 1 week!